Field-Trapping of Three Lepidopteran Fruit Pests with Sex Pheromone Traps in Korean Apple and Peach Orchards

Field-Trapping of Three Lepidopteran Fruit Pests with Sex Pheromone Traps in Korean Apple and Peach Orchards

Kyung Saeng Boo, Jin Kyo Jung and Kyung Sik Han

Insect Physiology Lab., Dept. Agric. Biol., Coll. Agric. & Life Sciences, Seoul National University

ABSTRACT. Synthetic sex pheromones have never been commercially used in Korea yet. But several side effects of synthetic organic pesticides are now causing both consumers and farmers to find better ways to control agricultural insect pests. One of these ways is to use sex pheromones for monitoring and/or directly controlling insect pests. This report is concerned about research work, conducted for last three years, on the possibility of using sex pheromones against apple fruit insect pests.

In Carposina sasakii females, the two known compounds, (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one, were detected from their abdominal tips. But, in field-trappings, lures containing only (Z)-7-eicosen-11-one showed the best attractiveness. In Grapholitha molesta, the abdominal tip extract of virgin females contained (Z)-8-dodecenyl acetate, (E)-8-dodecenyl acetate, (Z)-8-dodecenol and dodecanol. However, in field-trappings, the first three compounds, except for dodecanol, showed the maximum attractancy at the ratio of 95:5:1 in the order listed above. In Dichocrocis punctiferalis, (E)-10-hexadecenal and (Z)-10-hexadecenal of the known components were detected. The best response of males to various sex pheromone blends was obtained at the 70:30 ratio of (E)-10-hexadecenal and (Z)-10-hexadecenal for hairpencil extrusion and at the 80:20 ratio for upwind flying response. The maximum field-attractiveness was obtained at 70:30＃80:20 from several tests in peach and chestnut orchards.

A series of field experiments were then conducted to see whether there is a possibility of using a single lure containing all the sex pheromone components of three species for their monitoring. Males of C. sasakii were attracted equally well to lures mixed with sex pheromones of the other two species just as to a lure containing its own sex pheromone only. Males of G. molesta were equally attracted to lures mixed with sex pheromones of its own and of D. punctiferalis, but slightly less to lures containing also sex pheromones of C. sasakii. But capturing males of C. sasakii or of G. molesta showed an almost similar fluctuation pattern among various blends composed of sex pheromones of the three species. We need more studies in the case of Dichocrocis punctiferalis species, since the number of its males trapped in our field traps was not big enough to show any tendency yet.

Key words: Carposina sasakii, Grapholitha molesta, Dichocrosis punctiferalis, sex pheromone, field trapping

INTRODUCTION

For past several years, Korean farmers have faced the necessity to reduce the amount of organic synthetic pesticides to be sprayed in order to protect natural enemies, to cut down any residues of organic pesticides and to economize the production costs in their farms, especially in the cases of apple and peach orchards. The main pests in the orchards were fruit pests such as Carposina sasakii, Grapholitha molesta and Dichocrocis punctiferalis. A conventional method to monitor these pests is to count the number of their larvae in damaged fruits, but it is very inconvenient and costly to use. Therefore it is absolutely necessary to develop a convenient and economical way to monitor their population fluctuation. That was the main impetus for us to look at their sex pheromone compositions and to find the best blends for attracting their males in the fields.

The sex pheromone components of C. sasakii female have been known as (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one and their optimal blend for male attraction in fields has been reported to be 100:5 or 100:0 in Japan (Honma et al, 1978; Shirasaki et al, 1979; Tamaki et al, 1977). In G. molesta (Z)-8-dodecenyl acetate (Z8-12:Ac), (E)-8-dodecenyl acetate (E8-12:Ac), (Z)-8-dodecenol (Z8-12:OH) and dodecanol (12:OH) have been detected and the blend in field was 93.3:6.7 for Z8-12:Ac and E8-12:Ac or 100:6:30 for Z8-12:Ac, E8-12:Ac and Z8-12:OH in the USA (Beroza et al, 1973; Card諗et al., 1979; Linn and Roelofs, 1983; Roelofs et al, 1969). In D. punctiferalis, (E)-10-hexadecenal (10-16:Al) and (Z)-10-hexadecenal (Z10-16:Al) have been detected and the optimal blend was 90:10 in Japan and 100:8 in China (Konno et al, 1982; Liu et al., 1990). However, these results cannot be directly used in Korea, because there is a possibility of some geographical variations in optimal blends as shown in Heli

coverpa assulta (Cork et al, 1992) and Phyllonorycter ringoniella (Boo and Jung, 1996). Therefore, this research has been initiated to establish the optimal blends for best field attraction of males in the three fruit pests in Korean orchards (Boo et al, 1996).

RESULTS AND DISCUSSION

1. Carposina sasakii Matsumura

Upwind flying response of virgin males to virgin females was observed in a bell-shaped glassware where virgin males and females were released (Fig. 1). The males showed the maximum response in their upwind flight behavior towards virgin females between the 4th and 5th hour of scotophase. The mating rate of the adult pairs was also observed in a plastic cage with the maximum rate found between the 5th and 6th hr during the scotophase. The abdominal tips of virgin females were extracted with n-hexane between the 3rd and 4th hour of the scotophase and the extract was analyzed on GC to show both components, (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one.

Fig. 1. An experimental set-up in order to observe the upwind flying response of male moths to females or sex pheromone (DW: distilled water).

Then field male trapping experiments were conducted in peach and apple orchards in Suwon and Daegu regions. Lures containing various blends of (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one dissolved in n-hexane were placed in wing-type sticky traps. Rubber septum of control trap was impregnated with only n-hexane. The traps were hung out beneath the branches of trees 1.5-2 m above the ground. In one assay, a Japanese commercial product (CN, Takeda Co.) baited with (Z)-13-eicosen-10-one for trapping of C. sasakii was compared with the various blends of synthetic sex pheromone. The best capturing efficacy of sex-pheromone mixtures, in the range from 100:0 to 80:20 of (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one, was shown in the ratio of 100:0 (Fig. 2). The Japanese product showed a higher capturing efficacy than other 3 mixtures but showed a lower efficacy than a lure containing (Z)-7-eicosen-11-one only in one

Fig 2. Mean number of Carposina sasakii males caught in stiky traps baited with different blends of (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one in apple or peach orchards in 1994. Total amount of components loaded in each rubber septum was 1孚.

〨 Apple orchard (Jun. 2 - Jul. 29, Daegu)

﹤ Peach orchard (Jun. 20 - Jul. 30, Suwon)

〤 Peach orchard (Jun. 20 - Jul. 30, Suwon)

CN : A Japanese product (Takeda Co.) for attracting C. sasakii loaded with 3孚 of (Z)-13-eicosen-10-one.

peach orchard. In subsequent field trappings with chemical ratios from 100:0 to 100:5, no significant difference was observed in capturing of males (Fig. 3), though it was reported that the trapping efficacy was enhanced by addition of (Z)-7-nonadecen-11-one in Japan (Honma et al, 1978). Therefore, only (Z)-eicosen-11-one may be the optimal component for male attraction in Korean fields.

Fig. 3. Mean number of C. sasakii males caught in sticky traps baited with different blends of (Z)-7-eicosen-11-one and (Z)-7-nonadecen-11-one in peach orchards in 1994. Total amount of components loaded in each rubber septum was 1孚.

〨 Jun. 30 - Jul. 23, Suwon

﹤ Jul. 26 - Aug. 24, Namyang

〧 Aug. 19 - Aug. 24, Suwon

2. Grapholitha molesta (Busk)

In G. molesta, the calling behavior and mating rate in virgin adults released into a plastic box were observed. The calling behavior of females started from 4 hrs before the light-off and reached a peak 1 hr before the light-off, but ceased immediately after the light-off. The number of mating pairs also gradually increased and reached to a peak at 1 hr before the light-off. So the abdominal

Fig. 4. Mean number of G. molesta males caught in sticky traps baited with different blends of Z8-12:Ac and E8-12:Ac in two different peach orchards (〤: Jul. 20-Aug. 23 and 〧: Jul. 20-Aug. 24) located at Suwon in 1994. Total amount of components loaded in each rubber septum was 1孚.

Fig. 5. Mean number of Grapholitha molesta males caught in sticky traps containing Z8-12:Ac (95%) and E8-12:Ac (5%) with addition of Z8-12:OH from 0 to 10% at a Suwon peach orchard (Sep. 23 - Oct. 3, 1994). Total amount of components loaded in each rubber septum was 0.5孚.

tips of virgin females were excised 1 hr before the light-off and extracted with n-hexane for one hour. The extracts were analyzed on GC to reveal four components, Z8-12:Ac, E8-12:Ac, Z8-12:OH, 12:OH.

Field-trapping assays with synthetic sex pheromone were carried out in some peach orchards in Suwon. In the first experiments, Z8-12:Ac and E8-12:Ac in the various chemical blends between 100:0 and 90:10 were dispensed in rubber septa. Trapping efficacy was the highest in the 95:5 dispenser (Fig. 4). In a subsequent test, in which the chemical blends of Z8-12:Ac and E8-12:Ac were held at 95:5, and a small amount of Z8-12:OH was added to it, the maximum attractancy was shown in the lure with 1% of Z8-12:OH to the total amount (Fig. 5). In the third test, in which the ratio of Z8-12:Ac, E8-12:Ac and Z8-12:OH was held 95:5:1 and the various amounts of 12:OH were added to it, the maximum attractiveness was got in the lure without 12:OH (Table 1). In conclusion, the optimal blend for attracting G. molesta males seemed to be the ratio of 95:5:1 for Z8-12:Ac, E8-12:Ac and Z8-12:OH.

Table 1. Effect of 12:OH added to 0.5 孚 of Z8-12:Ac/E8-12:Ac/Z8-12:OH = 95/5/1 in attractancy of G. molesta males caught in sticky traps (peach orchard, May 15 - May 27, 1995, Suwon)

3. Dichocrocis punctiferalis (Guen餖)

The virgin adult pairs were released into a cage to observe the peak time of calling behavior and mating. The highest mating rate of adults was seen at the 5th hr after the light-off and the highest hairpencil extrusion rate at the 4th hr after the light-off. Around the mating time the abdominal tips of virgin females were extracted with n-hexane and then the extract was analyzed on gas chromatograph. The retention times of two peaks were coincided with those of the synthetic E10-16:Al and Z10-16:Al (Chemtech).

The responses of hairpencil extrusion and male flying upwind to the various sex pheromone blends were observed with males released into the set-up of Fig. 1. The maximum response was

Fig. 6. Flying upwing (﹤) and hair pencil extrusion (〧) response of Dichocrocis punctiferalis males to various blends of E10-16:Al and Z10-16:Al.

Fig. 7. Mean number of D. punctiferalis males caught in sticky traps baited with different blends of E10-16:Al and Z10-16:Al in apple and peach orchards in 1994. Total amount of components loaded in each rubber septum was 1孚.

﹤ Apple orchard (Jun. 1 - Jul. 29, Daegu)

〧 Peach orchard (Aug. 2 - Aug. 24, Namyang)

〤 Peach orchard (Aug. 2 - Aug. 24, Suwon)

observed when the ratio of E10-16:Al and Z10-16:Al was 70:30 in hairpencil extrusion experiment and 80:20 in the upwind-flying experiment (Fig. 6). More optimal blends for attractiveness to males were tested in apple, peach and chestnut orchards. In a field test, the stability of synthetic pheromones was tested using tocopherol and butylated hydroxytoluene as antioxidants. Initial and subsequent tests showed that males were attracted strongly when the ratio of E10-16:Al and Z10-16:Al was between 70:30 and 80:20 (Fig. 7, Table 2). More males

Table 2. 申otal number of D. punctiferalis males caught to sex pheromone traps baited with various blends of synthetic E10-16:Al and Z10-16:Al (1995)

A. Suwon peach orchard, Aug. 16 - Sep. 19) (2 孚 of sex pheromone loaded per lure)

B. Suwon peach orchard, Aug. 16 - Sep. 19) (2 孚 of sex pheromone loaded per lure)

C. Jinju chestnut orchard, Jul. 14 - Sep. 2) (0.5 孚 of sex pheromone loaded per lure)

Lures were exchanged with new lures 2 times during the monitoring period.

D. Jinju chestnut orchard, Jul. 14 - Sep. 2) (0.5 孚 of sex pheromone loaded per lure)

Lures were exchanged with new lures 2 times during the monitoring period.

E. Jinju chestnut orchard, Sep. 14 - Oct. 6) (2 孚 of sex pheromone loaded per lure)

Lures were exchanged with new lures 2 times during the monitoring period.

were attracted to the lures containing butylated hydroxytoluene than any other lures, showing the effect of an anti-oxidant (Fig. 8). However, since the number captured was so small, it remained to find the optimum ratio for best attraction of males in the fields.

Fig. 8. Mean number of D. punctiferalis males caught in sticky traps baited with different blends of E10-16:Al and Z10-16:Al with or without an antioxidant, butylated hydroxytoluene or tocopherol, in a chestnut orchard in 1994. Total amount of components loaded in each rubber septum was 1 孚.

﹤ : control, 〧 : Butylated hydroxytoluene added, 〤 : Tocopherol added

4. Field trappings of the three pest insects by mixed sex pheromone lures

The sex pheromone components of the three moth species were mixed in combination, based on the blends showing the best field-attractancy to each moth species (Table 3). The lures were absorbed into a rubber septum and bound to the sticky traps which were suspended from the fruit trees in apple or peach orchards. The captured males were counted at the interval of 5 days and the lures were exchanged with fresh ones every 15 days.

Table 3. Chemical composition of sex pheromone lures for each species used in field-trappings.

Table 4. Total number of C. sasakii males caught in traps baited with combination mixtures of synthetic sex pheromone from C. sasakii, G. molesta and D. punctiferalis

The fluctuation pattern in the number of C. sasakii males captured in the traps with its own sex pheromone only was similar to that with the traps with sex pheromones of the other one or two species combined. And the total numbers captured were also similar among treatments showing that C. sasakii males were not affected by sex pheromone components from the other two moth species in attractancy to its own sex pheromone (Table 4, Fig. 9).

Fig. 9. Trapping pattern of C. sasakii males in traps having its own sex pheromone component only or combination mixtures of synthetic sex pheromone from the other two species, G. molesta and D. punctiferalis.

Fig. 10. Trapping pattern of G. molesta males in traps having its own sex pheromone component only or combination mixtures of synthetic sex pheromone from the other two species, C. sasakii and D. punctiferalis.

In the number of G. molesta males captured, the fluctuation pattern was similar among traps with sex pheromone components of its own and of the other one or two species added. All treatments also had 5 peaks (Fig. 10). The total number of G. molesta males captured were also similar among those traps in the apple orchard, but, in the peach orchard, those traps containing sex pheromones components of C. sasakii were lower than those in traps without C. sasakii sex pheromone components (Table 5). This negative effect was not seen in the case of traps containing sex pheromone components of D. punctiferalis.

Table 5. Total number of G. molesta males caught in traps baited with combination mixtures of synthetic sex pheromones from G. molesta, C. sasakii and D. punctiferalis

In D. punctiferalis males, the number caught in traps with its own sex pheromone only was always higher than those in traps containing the sex pheromone components from either one or two other species. However, the fluctuation patterns could not be compared among the treatments because the total number captured was too small (Table 6).

From the fluctuation pattern, the sex pheromones of C. sasakii and G. molesta might be formulated in a single lure for their monitoring at least.

Table 6. Total number of D. punctiferalis males caught in traps baited with combination mixtures of synthetic sex pheromones from D. punctiferalis, C. sasakii and G. molesta

FUTURE PROSPECT

Some results in our sex pheromone research in fruit pests showed that their sex pheromones may be utilized directly for their monitoring in apple and/or peach orchards in Korea. For example, a single component, (Z)-7-eicosen-11-one, could be enough in preparation of lures for monitoring of C. sasakii. The three components of the sex pheromone for G. molesta may be used for monitoring its population too. If the monitoring of its population is the only purpose, Z8-12:OH can be omitted from the formulation. An economical way of monitoring population of these fruit pests would be to use a single trap containing sex pheromone components for all three species. Our experiment results demonstrate that it is quite possible for the two species, C. sasakii and G. molesta, at least. Of course, in this case, another professional knowledge is required, namely an easy and efficient way of their classification from those specimens caught in sticky traps, which is not an easy task to ordinary farmers.

We, however, need more studies in the case of the third species, D. punctiferalis, even though we are quite confident that its sex pheromone blend is optimal.

We are going to field-test the blends for monitoring their populations for a few more years and eventually to see whether our blends can be used in direct control of those fruit pests with mating disruption technique. The results may contribute to reducing amount and kinds of pesticides to be used and to cut down the cost producing safe apples and peaches in Korea.

Acknowledgments. This article is based on the research carried out with the financial assistance from Rural Development Administration. We would also like to express our sincere thanks to the staffs of Taegu Apple Research Institute including Dr. Soon Won Lee for their cooperation in field screenings.

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